1. Field of the Invention
The present invention relates to a sensing system, and particularly to a sensing system having a mirror component and a locating method thereof.
2. Description of the Related Art
Nowadays, a touch function has been one of necessary functions of many electronic devices. A touch system is an important component to achieve the touch function. Generally, a familiar type of the touch system is, for example, a resistive touch system, a capacitive touch system or an optical touch system. The electronic devices can be equipped with various touch systems in accordance with the various demands.
FIG. 1 is a schematic view of a conventional optical touch system. Referring to FIG. 1, the conventional optical touch system 100 includes a light guide module 110, a light source module 120 and a image sensor module 130. The light guide module 110 includes four light reflecting bars 112a, 112b, 112c and 112d arranged along four sides of a rectangle. The area in the rectangle defines a sensing area 114. The light source module 120 includes three light emitting components 122a, 122b and 122c. The light emitting component 122a is disposed between two neighboring ends of the light reflecting bar 112a and the light reflecting bar 112b, the light emitting component 122b is disposed between two neighboring ends of the light reflecting bar 112b and the light reflecting bar 112c, and the light emitting component 122c is disposed between two neighboring ends of the light reflecting bar 112a and the light reflecting bar 112d. The light source module 120 is configured for emitting light to the four light reflecting bars 112a, 112b, 112c and 112d. The four light reflecting bars 112a, 112b, 112c and 112d are configured for reflecting the light from the light source module 120 to irradiate the sensing area 114. The image sensor module 130 includes three image sensors 132a, 132b and 132c. The image sensor 132a is disposed two neighboring ends of the light reflecting bar 112a and the light reflecting bar 112b, the image sensor 132b is disposed two neighboring ends of the light reflecting bar 112b and the light reflecting bar 112c, and the image sensor 132c is disposed two neighboring ends of the light reflecting bar 112a and the light reflecting bar 112d. 
The image sensor module 130 is configured for detecting a pointer (i.e., a light blocking object) in the sensing area 114, thereby calculating a location (i.e., coordinates) of the pointer in accordance with the information sensed by the image sensor module 130. For example, when two pointers are located in the sensing area 114, each of the image sensors 132a, 132b and 132c senses two dark points. In theory, the location of the pointer can be calculated using any two sensed dark points. However, in some cases, one of the image sensors 132a, 132b and 132c maybe sense only a dark point.
For example, when two pointers A and B are located in the sensing area 114, the image sensor 132a can sense two dark points A1 and B1, the image sensor 132b can sense two dark points A3 and B3, and the image sensor 132c can sense two dark points A3 and B3. The dark points A1, A2, and A3 are caused by the pointer A, and the dark points B1, B2, B3 are caused by the pointer B. However, because the dark point A1 is overlapped with the dark point B1, in fact, the image sensors 132a only senses one dark point. Thus, the locations of the dark points A1 and B1 calculated using a gravity center calculating method will generate an inaccuracy, thereby causing a deviation of the gravity center.
As above-mentioned, when the locations of the pointers A and B are calculated by using the dark points A1, B1, A2 and B2 sensed by the image sensors 132a and 132b, the location of one of the pointers A and B can be calculated by using a straight line L1 and a straight line L2, and the location of the other of the pointers A and B can be calculated by using the straight line L1 and a straight line L3. However, due to the deviation of the gravity center mentioned above, a large error between the calculated locations of the pointers A′ and B′ and the actual locations of the pointers A and B will generate. Similarly, when the locations of the pointers A and B are calculated by using the dark points A1, B1, A3 and B3 sensed by the image sensors 132a and 132c, the same problem is existed.
Additionally, when the locations of the pointers A and B are calculated by using the dark points A2, B2, A3 and B3 sensed by the image sensors 132b and 132c, the location of one of the pointers A and B can be calculated by using the straight line L2 and a straight line L5, and the location of the other the of pointers A and B can be calculated by using the straight line L3 and a straight line L4. However, because a slope of the straight line L2 is almost equal to that of the straight line L5, and a slope of the straight line L3 is almost equal to that of the straight line L4, a large error between the calculated locations of the pointers A″ and B″ and the actual locations of the pointers A and B will generate.
Moreover, the conventional optical touch system 100 has a blind zone. The blind zone refers to an area in the sensing area 114 where the dark point caused by the pointer can not be sensed by the image sensor 132b or the image sensor 132c of the image sensor module 130 and the location of the pointer can not be calculated. For example, as shown in FIG. 3, a sensing range of the image sensor 132a covers the light reflecting bars 112a and 112d. An interval for disposing the image sensor 132c exists between the light reflecting bar 112a and the light reflecting bar 112d. Because the image sensor 132c can not reflect the light, the image sensor 132b can not sense a pointer C in an area 150. Thus, the area 150 is the blind zone of the image sensor 132b. In addition, when a pointer D is located in the area 150 partially, the image sensor 132b can not sense a dark point caused by the pointer D accurately. Thus, a location of the pointer D can not be calculated accurately yet. It is noted that the image sensor 132c has the same problem.